1. Field of the Invention
The subject invention relates to an injection molding exhaust manifold having a ceramic liner and method of making the same.
2. Description of the Prior Art
Generally, catalytic converters used in the automotive industry, are usually heated by the engine exhaust gases. It is critically important to minimize the amount of a residual heat of the exhaust gases of an internal combustion engine to provide for highly efficient and effective catalytic converter that may reduce the emission levels of the engine.
Numerous, techniques for insulating exhaust manifolds and for providing other means to speed up light off have been suggested and known in the automotive industry today. One of the techniques known is a cast iron molding, disclosed in the U.S. Pat. No. 5,018,661 to Cyb, that shows a cast manifold comprising first and second sections cast in place from a metal to form a housing of the manifold. Hence, cast molded exhaust manifolds are heavy and increase the overall weight of the vehicle. The U.S. Pat. No. 5,682,741 to Augustin et al. and U.S. Pat. No. 5,419,127 to Moore, III show a welded tubing exhaust manifolds that have less mass, but are complicated and expensive to manufacture. Additionally, a double-walled welded tubing exhaust manifolds have been suggested, with an air gap between the walls, as shown in the Moore Patent cited above. Hence, double-walled exhaust manifold may be not cost effective, they are still complex to manufacture.
The related art also provides for other examples of exhaust manifolds being cast molded from a liquid metal having ceramic particles for use on vehicles. One such example is shown in U.S. Pat. No. 5,223,213 to Kamimura et al. The Kamimura Patent discloses an exhaust manifold having ceramic particles integrally formed within the exhaust manifold. However, the liquid metal used for casting the exhaust manifold may include defects, which reduces the strength of the exhaust manifold.
The approaches disclosed in the prior art patents, cited above, are expensive and add weight. Injection molding is a preferred process for manufacturing complex shaped parts from metal and ceramic powders. One such method is shown in U.S. Pat. No. 6,056,915 to Behi et al. The Behi Patent discloses method of making tools from injection molding procedures and includes the steps of inserting a mold into an injection molding apparatus, injecting powder metal feedstock into the mold, debinding the part for forming a green body, and sintering the part to form a completed part. However, the Behi Patent does not allow for multiple components to be combined into a single unitary piece.
Although the prior art patents disclose different designs of exhaust manifolds and methods of making the same, one of the opportunities of continuous development and research is the area of a more advanced design of an exhaust manifold and process of making the same that may provide for additional weight reduction and dissipation of heat energy contained in the exhaust thereby increasing the efficiency of the catalytic converter, and reduction of the manufacturing cost of the catalytic converter since the size of the catalytic converter may be reduced with increased efficiency. Still another area of continuous development and research is the area of a manifold design that may eliminate seams on the outer shell wherein the liner or insert is encapsulated by the outer shell continuously extending about the liner.